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S. D. FIELD.

QUADRUPLEX TELEGRAPH. No. 254,297. Patented Feb. 28.1882.

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QUADRUPLEX TELEGRAPH.

No. 254,297. Patented Feb. 28,1882.

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3% i0 fitter/nu N. PETERS. PhMo-Lilhognphur. Washm mn. D. C.

Unitas STATE PATENT OFFICE. I

STEPHEN D. FIELD, OF NEW YORK, 'N. Y.

QUADRUPLEX TELEGRAPH.

SPECIFICATION forming part of Letters Patent No. 254,297, dated February 28, 1882.

Application filed October 20, 1881. (No model.) i i 7 To all whom it. may concern:

Be it known that I, STEPHEN D. FIELD, a citizen of theUnitcd States, and a resident of the city, county, and State of New .York, have invented certain new and useful 1m provcments in Quadruplex Telegraphs, of which. the following is a specification.

My invention consists generally in the combination, with a main line, of two independent receiving neutral relays, one of which is an or- V dinary relay of the usual construction, while the other is provided with a yielding contactlever, which carries a stop, against which the main armature-lever plays, in lieu of the usual fixed stop. Thiscontactdeverisnormally held bya spring against a fixed stop, and the local circuit of the receiving-instrument is made to traverse the armature-lever, the contact-lever, and the fixed stop. An improved adjusting device is provided, whereby both the armature and the contact levers may be simultaneously adjusted. Two keys or transmitters are placed at'the sending-station, and these are connected with two 'main batteries of unequal electro-v motive force,'the connections of the keys being s o arranged that when both arein a position of rest a current flows over the main line," which is just sufficient to maintain the aijlna tore-lever in contact with the yielding step at the receiving-station. By the depression of one or the other of the keys separately or of both of them together the current is interrupted, or currents of different strengths are transmitted over the line in such manner that the movement of each key is properly responded to by the respective sounders or other receivingdnstruments which are placed in local circuits at the receiving-station. v

For the sake of simplicity I have shown my invention as applied to the transmission ot'two independent communications simultaneously in the same direction over a single conductor, constituting what is technically termed a doplex, or, more properly, a diplex telegraph; but it is to'be understood that any of the wellknown methods of equating or balancing may be applied to my invention or combined with it in a manner well understood, so as to enable-four distinct,communications-two in each direction-to be transmitted over the said conductor simultaneously.

In the accompanying drawings, Figures 1, 2, 3, and 4 are diagrams illustrating my inventionand its operation under different conditions, showing its application to the transmission oftwo communications simultaneously in the same direction. Figs.5 and 6 are drawings showing certain details of the invention.

In the drawings the main telegraph-line, consisting of an insulated telegraphic conductor extending from station A to station B, is shown at a. These two stations are assumed to be situated at a considerable distance from each other. At station A two independent transmitters are placed in connection with the line, as shown in the figures, where they are respectively designated as l and 3. These transmitters may consist of ordinary key-levers worked directly by the finger of the operator, as shown in the several figures, or they may be operated by an electromagnet, local battery, and independent finger-key in a wellknown manner.

The transmitters l and 3 are each provided with circuit-preservin g coutact-sprin gs or other equivalent devices of well-known construction,- so that when either transmitter is actuated a current may be transferred from one branch of the circuit to another without at any time interrupting the same. The contact-points which form the terminals of the respective branch circuits may conveniently be desi gnated as resting and working contacts, respectively, meaning by the former the contact which the circuit-sprin g bears a gainstwhen the transmitter is elevated or in its normal position, and by the latter the contact which it bears against when the transmitter is depressed, as in the act of transmitting a signal.

The transmitting-batteries are shown at 5 and 6. These arerespectivelyplacedin branch circuits, and are so connected with the respective keys or transmitters 1 and 3 that their cur-- rents may be thrown upon the line either separately or together without at any time interrupting the circuit.

it will be more convenientin explaining the operation of the system to consider the batteries 5 and 6 as two sections of one and the same battery, which they in fact are, the section 6 being preferably so constructed and ar- IOC ranged that its total electro-motive force will be about twice as great as that of the section 5. For the sake of illustration we may assume the section 6 to consist of twelve cells or elements. The number of cells required in practice will necessarily vary in each particular case, as it must be made proportionate to the length of line through which the apparatus is designed to be operated, or to the resistance to be overcome by the electric currents; but it is essential to maintain in every case substantially the same relative proportion between the electro-motive forces of the two sections of the battery. A

Considering in the first place the operation of the transmitters 1 or 3 when they are employed for simultaneously sending two independent sets of signals, as in quadruplex working,-it will be observed that they may occupy four different positions or relations, as follows: first, both transmitters up; second, transmitter 1 down and transmitter3 up 5 third, transmitterl up and transmitter3 down; and, fourth, both transmitters down. The organization of the several branch conductors between the transmitters 1 and 3, the batteries 5 and 6, and the line a is such that four difl'erent electrical conditions may be produced upon the line, depending respectively upon the positions of the keys, as hereinbefore stated. In the first position referred to, which is that shown in Fig. 1 of the drawings, both transmitters are up or in a position of rest and a current from the battery 5 passes over the line a.

The circuit through the transmitting apparatus may be traced as follows: from the earth atg at station A by the wires 1) andc to the negative pole of the battery-section 5; thence from the positive pole of said battery by the wire (1 to the lever 7 of the transmitter 3; thence by the circuit-spring 8, wire 6, lever 9 of trans mitter 1, resting-contact 10 upon said lever, circuit-spring 11, and line-wire a to station B. Thus when the transmitters are in'their normal' positions, as shown in" Fig. 1, a positive currentfrom six cells traverses the line from the battery 5, which for convenience of explanation may be assumed to have an electro-motive force of six volts. It the transmitter 1 alone be depressed, the connection of the branch circuits at the -sending-station is changed,and they assume the relation shown in Fig. 2. The circuit may now be traced as follows: from the earth at g by the wires b and f, resting-contact 12, circuit-spring 13, wire h, negative pole of battery-section 6, and thence from the positive pole of said batterysection by wire '5 to working-contact 14 of transmitter 1, and thence by circuit-spring 11 and wire a to station B. Thus transmitter 1, when depressed, sends to line a positive current having an electronictive force of twelve volts from the battery-section 6. If, new, the transmitter 3 be alone depressed, the transmitter 1 remaining at rest, the circuit will be as follows, referrin g to Fig. 3: from the earth at g by the wires 1) andfto the resting-contact12, thence by circuit-spring 8 and wire 6 to the lever 9 of transmitter 1, thence by the resting-contact 10 of said transmitter and circuit-spring 11 to the line-wire a, and thence to station B. In this position of the keys no battery whatever is in circuit at the transmitting-station, a direct circuit being formed between the earth at g and the line at a, and there will consequently be no current upon theline. In case both transmitters 1 and 3 are depressed simultaneously the route of the current will be as follows, (see Fig. 4:) from the earth at g by the wires b and c to the negative pole of the battery-section 5, and from the positive pole of said battery-section by the wire d to the lever 7 of transmitter 3, thence by circuit-sprin g 13 and wire h to the negative pole of battery-section 6, and from the positive pole of said battery-section by wire z to working contact 14, and thence by circuitspring 11 and linewire a to station B. In this case both battery-sections, 5 and 6, are in circult, and a positive current is transmitted to line having an electro-motive force of eighteen volts. The effect of these different strengths of current upon 1 the receiving apparatus at station B will next be considered.

15 and 16 are electro-magnets, which actuatetwoindependent relays, 2 and 4, which electro-magnets are included in series in the main line. Each of the relay-magnets 15 and 16 is provided with a neutral armature mounted upon a pivoted lever in the usual manner, as shown at 18 and 19, and adjustable retractile springs'20 and 37. The lever 18 is also provided with the usual adjustable stops, 22and 23. A sounder, register, or other equivalent reeeivinginstrument, 24, is included with a local batter-5 ,25, in a local circuit traversing the armature-lever 18 and the contact-stop 22, as

indicated by the dotted line in the figures. The receiving apparatus 4is provided, in addition, with a supplementary contact-lever, 26, which'is pivoted at 27, and is normally held against a fixed stop, 28, by means of an adjustable-spring, 29, which is preferably made to act through a device to be hereinafter described.

The workiug-contact 17 of the armature-lever 19, instead of being stationary, is mounted IIO upon the extremity of the pivoted contact-lever'26, and a fixed stop, 30, is placed in the rear of the latter at such a distance as to permit the contact-lever 26, which is held against the stop by the spring 29, to yield slightly under the application of sufficient force, and thus to fall back until arrested by the said stop. The relay 4 is also provided with a sounder or other equivalent receiving-instrument, 32, which is placed in circuit with a local battery, 31. This local circuit (indicated by dotted lines) is opened and closed by the armature-lever 33 of a local relay-magnet, 34. The electro-magnet 34 is included in an intermediate local circuit which is actuated by the local battery 35,- and traverses the armature-lever 19, the contactlever 26, and the fixed stop 28, as indicated by the dotted lines.' The object of the interme-. diate local circuit is to reverse the signals between the relay 4 and the sounder 32;

The retractile force which is exerted upon the armature-lever 19 and the contact-lever 26 in opposition to the attractive force of the elec tro-magnet 16 must be accurately adjusted, 'so as to permit the armature 18 of relay2 to respond to a strength of current produced by an elec: tro-motive force of twelve or more volts at the transmitting-station, but not tocurrents of less strength. The armature-lever 19 of relay 4 must respond primarily to a current having an electro-motive force of six volts at the transmitting-station, which will thus act to bring it forward against the yieldingstop on the con; tact-lever 26, while the adjustment of the contact-lever 26 must be such as to permit it to yield only when the force exerted by the armature 19 under the influence of the current is produced by the electro-motive force of not less than eighteen volts at the sending-station.

The effect of the several strengths of current upon the apparatus at the receiving-station will be as follows: With both transmitters at rest or in their normal position (see Fig. 1) the current over the line will have an .electro-motive force of six volts. This will not be sutfi cient to overcome the tension of the spring 20 or to move the armature-lever 18, but will be just sufiicient to overcome the spring 37 and bring the armature-lever 19 against the contact-lever 26, although not-suflicient to cause the latter to yield. Hence the circuit of the intermediate local battery, 35, will be closed through thelocal relay 34, and the armature 33 of the latter will be attracted. As the independent local circuit which actuates the sounder 32 is completed through the back contact, 36, of the armature-lever 33, this latter local circuit will be kept open. Hence it will be understood that both the sounders 24 and 32 will be inactive. When the transmitter 1 alone is depressed, as in Fig. 2, a current of twelve volts is sent to line. This is sutficient to overcome the tension of the spring 20, and thus close the circuit of the local battery 25 and operate the sounder 24. It is not, however, sufticient to overcome the resistance of the yieldingcontact-lever 26 as determined by the spring29, and therefore the sounder 32 remains When the tran sinactive, as in the first case. mitter 3 is depressed, as in Fig. 3, no current whatever passes over the main line. Hence the armature-lever 18 of relay 2 remains on its back contact and the sounder 24 continues to be inactive. The armature-lever 19 of relay 4 also falls on its back contact, breaking the intermediate local circuit of battery 35 between thearmature-lever 19 and the contact-lever 26. The armature 33 of the local relay 34 therefore falls on its back contact, 36, closing the circuit of local battery 31 and actuating the sounder 32. When both transmitters 1 and 3 are simultaneously'depressed, as in Fig. 4, a current of eighteen volts is sent over the line. This overcomes the tension of spring 20 in relay 2 and actuates the sounder 24. It also causes the armature-lever 19 to overcome the resistance ofthe yielding contact-lever26 and spring 29, in addition to that of spring 37, and thus breaks the intermediate local circuit between the contact-lever 26 and the fixed stop 28, The breaking of the intermediate local circuit, as hereiubefore explained, closes the independent local circuit from the battery 31,and thus actuates the sounder 32.

In the diagrams Figs. 1, 2, 3, and 4 I have shown the armature-lever l9 and the contactlever 26 of the relay 4 as provided with independent adjustable retracting-springs 29 and 37. In practice I have found it to he a matter of more or less difficulty for the receiving operator to maintain the adjustment of these independent springs, especially when the insulation of the line is variable, in such a manner as to preserve at all times a proper relation between them, and thusinsure the proper workingof the apparatus. In order to avoid this difficulty I have devised the apparatus shown in detail, Fig. 5, inwhich I make use of an equalizing-bar, 38. To the extremities of this equalizingbar are attached two links or tension-rods of thin wire, 39 and 40, the, opposite ends of which are respectively attached to the contact-lever 26 and the armature-lever 19.

A retracting-spring, 41, the tension of which may be adjusted by a milled head and spindle,

42, inthe usualv manner, is attached to the equalizing-bar 38 atan intermediate point between the points of attachment ot'the links 39 and 40. The particular point at which the spring 41 is attached to the equalizing-liar 38 determines what proportion of the total tension of the spring shall be exerted upon the contact-lever 26 and the armat ure-leverl9, respect? ively. For example, in the operation of the apparatus as hereiubefore described, it is necessary that the mechanical resistanceoftered to the moving of the contact-lever 26 should be about three times as great as that offered to the moving of the. armature-lever19, and hence the spring 41 should be attached to-the equalizing-bar 38 by placing it in a notch of the bar atla pointdistant about one-fourth of its'length' from the end to which the link 39 is attached. The precise point of attachment of the spring 41 to the equalizing-bar 38 may bedetermined by experiment or otherwise for eachparticular instrument by moving italong the notched .bar, and when once fixed it will not need to be changed. The tension of the spring 41 will only require to be adjusted by the operator with reference to the varying attractive force developed in the electro-magnet 16 in accordance with the electrical condition of the line, while the proportionate distribution of the totalretractile force of the spring 41 between the armature-lever 19 and the contact-lever 26 will be automatically effected by the apparatus described with the utmost nicety.

It will be understood from the description which has been given of the manner in which the relay2 at the receiving-station is actuated that it is required to perform a particular op- (1 flerent strengths of current in the main circuit, one of which is considerably greater than the other, and hence that it becomes necessary to so adjust the tension of the retracting-spring 20 that the relay will perform its functionequally well whether under the influence of the greater or the lesser strength of current. On the other hand, the electro magnet 16 of the relay 4 is required to perform certain operations which difl'er according to the strength of current passing through its coils. In order to adapt these two electro-magnets l5 and 16 more perfectly to the different classes of work required from them, I prefer to construct them as hereinafter described, and particularly illustrated in Fig. 6. i

The electro magnet 15is provided with coils or bobbins the length of which is preferably about twice as great as their diameter, while the electro-magnet 16, although the number of convolutions in its coils is approximately the same, has bobbins which are much shorter and of greater diameter. The core of electro-magnet 16 is made short and of large diameter. The core of electro magnet 15 is made of comparatively small diameter, but of greater length. It is advisable to so proportion the respective cores of the electromagnets 15 and 16 that the area of the crosssection of the former shall not exceed one-half that of the latter. Important advantages result from this organization, inasmuch as the magnetic intensity developed in the core of any electro-magnet (other things being equal) is in proportion to the number of convolutions in the coil through which the current flows. Hence an equal amountot' magnetism will tend to be developed by a given current in both the electro-magnets'15 and 16; but owing to the smaller sectional area and mass of the core of the electro-magnet 15, it reaches itsmaximum magnetic intensity through the influence of a current of much less strength than that required to bring the electro-magnet 16 to its point of maximum intensity. The number of convolutions is :such that a current from the larger section of the battery at the sendingstation will be just suflicient to raise the core of the electro-magnet 15 to its condition of maximum magnetic intensity-in other words to bring it to a condition of magnetic saturation. Hence, it the current be. further augmented by the addition of the smaller section of battery, the attractive force of the electromagnet 15 will not be enhanced, nor will there be any perceptible changein theaction of its armature. On the other hand, the current produced by the larger section of the battery will not be sufficient to magnetize the greater mass in the core of the electro magnet 16 to a condition of saturation, and hence an increase in the current from the sending-station will be responded to by an increased attraction in the electro-magnet 16. v

I have found by experience that the best results arefproduced when the number of con volutions in the coils of the two electro-magnets are made approximately equal, while the sectional area of the cores of the magnet 16 is made twice or more times as great as that of the electro-magnet 15. It may also with ad vantage be made considerably shorter, although this is not absolutely essential.

I do not claim specifically the combination of an electro-magnet, an armature, an armature-lever, a yielding contact-lever normally held in contact with a fixed stop by a'spring, and a second electro-magnet for actuating a receiving-instrument which is included in a local circuit traversing the armature-lever, the contact-lever, and the fixed stop in succession, as I am aware that the said combination has heretofore been known and used. i

I do not claim the combination of a main line, two independent keys at the home-stre tion for varying the strength of currents transmitted over said line, and two locally independent neutral relays at the distant or receiving station, responding respectively to said keys.

I claim as my invention 1. The combination, substantially as hereinbef'ore set forth, of a key provided with one circuit-spring playing between a resting and a working contact, a key provided with two independent circuit-springs, each playing between a resting and a working contact, a main battery in two sections of like polarity, the firstiof which has greater electro-motive force than the second, a main line connected to the circuit-spring of the first key, a branch which unites the resting-contact of the first key with the first circuit-spring ot' the second key, a branch which unites the working-contactot' the first key with the second circuit-spring of the second key and includes the greater section of the battery, an earth branch connected to both the first restingcontact and to the second working-contact of the second key, and including the lesser section of the main battery, and a branch extending from the first working-contact and the second resting-contact of the second key to the earth.

2. The combination, substantially as hereinbefore set forth, of an electro-magnet, its armature and armature-lever, a yielding contactlever, an equalizing-bar having its extremities attached respectively to said armature and contact levers, and an adjustable retractor attached to and acting upon said equalizing-bar.

3. The combination, substantially as hereinbefore set forth, of two pivoted levers, an equalizing-barhavingits endsrespectivelyconnected with said levers, an electro-magnet for actuating said levers, a retractor attached to said equalizing-bar, and a device for regulating the normal tension of said retractor.

4. The combination, substantially as herein- IIO before set forth, of two pivoted levers, an equalizing-bar having its respective ends mechanically connected with said levers, an electromagnet for actuating said levers, a retractor attached to said equalizing-bar, a device for regulating the tension of said retractor, and means, substantially as described, for varying the point of attachment of the retractor upon the equalizing-bar.

5. The combination, substantially as hereinbefore set forth, of a main line, a main battery, devices, substantially such as described,for varying the strength of the current of said bat- 

